CF 1505I - Mysterious language again, seriously?

Rating: 2200
Tags: *special
Solve time: 1m 29s
Verified: yes

Solution

Problem Understanding

This is one of Codeforces's special problems. There is no conventional algorithmic input. Instead, contestants were given access to a language hidden behind the codename "Secret 2021" in the Custom Test environment and had to determine what real programming language it actually was.

After identifying the language, the task becomes extremely simple. The submitted program receives no input and must print the name of that language exactly.

The challenge is not computational. There are no arrays, graphs, strings, or numerical constraints to process. The entire problem revolves around reverse-engineering the hidden language provided by the contest system.

Because the input is empty, there are no size limits to analyze. The running time and memory consumption are effectively constant regardless of the submission environment.

The main source of wrong answers comes from identifying the language incorrectly or printing its name in a different format than expected.

Consider the empty input:

The correct output is the exact language name discovered from the hidden environment. A solution that prints a different capitalization, an abbreviation, or extra whitespace would fail even though it performs no computation.

Another potential mistake is attempting to read input. Since no input exists, such code may still work, but it serves no purpose and complicates an otherwise trivial solution.

The intended discovery for this problem was that "Secret 2021" is the language Clojure. Therefore the required output is:

Clojure

Approaches

A hypothetical brute-force approach would be to experiment with the hidden language environment, testing syntax from many candidate languages until one matches all observed behavior. Contest participants effectively performed this investigation outside the submitted program.

Once the language has been identified, there is no remaining algorithmic work. The optimal approach is simply to write a valid program in that language which outputs its own name.

The key observation is that the judge never provides input and never asks for any computation. The entire problem reduces to producing a fixed string.

Approach	Time Complexity	Space Complexity	Verdict
Reverse-engineer language manually, then print answer	O(1)	O(1)	Accepted
Print the discovered language name	O(1)	O(1)	Accepted

Algorithm Walkthrough

Determine which real programming language corresponds to the codename "Secret 2021" by investigating the provided execution environment.
Discover that the language is Clojure.
Write a valid Clojure program that outputs the string "Clojure".
Submit the program.

Why it works

The judge checks only the program's output. Since the correct language name is "Clojure", any valid program written in the hidden language that prints exactly that string will satisfy the specification. No input-dependent behavior exists, so a constant output is sufficient.

Python Solution

The actual accepted submission must be written in Clojure, not Python. Since this editorial template requests a Python section, we can express the same logic in Python as follows:

import sys
input = sys.stdin.readline

print("Clojure")

The program ignores input because none exists. It emits the required answer immediately. There are no loops, conditionals, or data structures because the output never changes.

Worked Examples

The problem contains no official samples because the input is always empty.

Example 1

Input:

Step	Action	Output
1	Start program
2	Print language name	Clojure

The execution demonstrates that the program's behavior is completely independent of input.

Example 2

Input:

Step	Action	Output
1	Start program
2	Print language name	Clojure

This second trace is identical because every test case is the same empty input.

Complexity Analysis

Measure	Complexity	Explanation
Time	O(1)	A single fixed string is printed
Space	O(1)	No data structures are allocated

The solution uses constant resources and easily satisfies the contest limits.

Test Cases

# helper: run solution on input string, return output string
import sys, io

def solve():
    import sys
    input = sys.stdin.readline
    print("Clojure")

def run(inp: str) -> str:
    old_stdin = sys.stdin
    old_stdout = sys.stdout

    sys.stdin = io.StringIO(inp)
    out = io.StringIO()
    sys.stdout = out

    solve()

    sys.stdin = old_stdin
    sys.stdout = old_stdout

    return out.getvalue().strip()

# empty official test
assert run("") == "Clojure", "official test"

# custom cases
assert run("") == "Clojure", "empty input"
assert run("\n") == "Clojure", "extra newline ignored"
assert run("random text\n") == "Clojure", "input is irrelevant"
assert run("1 2 3\n4 5 6\n") == "Clojure", "always prints fixed answer"

Test input	Expected output	What it validates
Empty input	Clojure	Official scenario
Single newline	Clojure	Ignores whitespace
Random text	Clojure	Output is independent of input
Multiple lines	Clojure	Constant behavior

Edge Cases

The first non-obvious case is the actual judge input, which is completely empty:

The algorithm performs no reads and immediately prints:

Clojure

This succeeds because the required answer does not depend on any external data.

Another case is receiving unexpected whitespace:

The program still prints:

Clojure

Since the solution never examines input, whitespace cannot affect the result.

A final case is accidental extra input:

abc
123

The program again outputs:

Clojure

The correctness condition depends only on producing the fixed language name, so any input content is ignored.